This invention relates in general to a photographic camera and particularly to a zoom lens assembly especially for a movie camera.
In a zoom lens assembly including a focussing ring, a zooming ring and a fixed-tube for supporting these rings and associated lenses, it is known that focussing is automatically adjusted at the hyperfocal distance in dependence on changes in the focal length which are brought about by the zooming operation. For example, reference should be made to the Japanese Patent Publication No. 33509/1971. Further, Japanese Utility Model Publication No. 34107/1972 discloses a structure for indicating in a viewing field of a finder provided in the camera whether or not the object is within the depth of field, thereby making it possible to indicate the range in which a sharp image is assured when the zooming is carried out with the focussing ring set at the hyperfocal position. In the former case in which focussing is automatically adjusted at the hyperfocal distance in dependence on changes in the focal length brought about by the zooming operation, it is certainly possible to take photographs without fear of the image being blurred due to the zooming in a relatively wide range of the constant focal length as set. However, this solution requires a very complex structure to be provided in an otherwise relatively small space available in the fixed-tube of the zoom lens assembly which, in turn, will necessarily become very expensive. On the other hand, in the latter case where merely the allowable range for photographing at the hyperfocal distance is indicated, there may arise a possibility that the indication might be overlooked by the camera operator who has to attend to other various information given during the photographing and the corresponding manipulations. This is particularly true in the case of an 8 mm. sound movie cameras for recording simultaneously both images and sounds, in which attention of the operator is often diverted from the focussing adjustment, resulting in blurred images, because of his being devoted to other adjustments and settings such as adjustment of the input level of sound, positioning of a microphone or the like in addition to the operations required for the optical system.